This paper presents a stratigraphic and paleontologic study of the Upper Cambrian exposed in three linear belts in the central Appalachians: (1) in the Nittany Arch region of southern Pennsylvania (Warrior and Gatesburg formations), (2) in the Shenandoah-Cumberland Valley of Virginia, West Virginia, Mary-land, and Pennsylvania (Elbrook and Conococheague formations), and (3) the Frederick Valley (Frederick limestone) of Maryland. Cambrian stratigraphy in the three areas is discussed, and a new member is named in the lower part of the Conococheague formation. A general facies change west to east from arenaceous dolomite (Gatesburg formation) to silt-laminated limestone (Conococheague formation) is indicated in the geosyncline.

Charles Butts' earlier correlation of the Warrior with the Elbrook and the Gatesburg with the Conococheague formation is found to be approximately correct on the basis of trilobite faunas. The paleogeographic significance of the stratigraphy is outlined on a regional isopachous-facies map.

Trilobites identified from the Warrior, upper Elbrook, and lowest Conococheague formations indicate a Dresbachian age for these beds. Trilobites of Franconian age from the middle Gatesburg and lower Conococheague formations show more complex relationships. The Ore Hill member of the Gatesburg formation contains in descending order the Conaspis and Elvinia faunizones, the latter replaced eastward in the Conococheague formation by a new trilobite facies fauna. The fauna is named for its most abundant trilobite, Pseudosaratogia magna, and in the Conococheague constitutes a lower Franconian faunizone equivalent to the Elvinia unit in the standard sequence. Trempealeauian trilobites are identified from the upper Conococheague formation.

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